1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus which has a high degree of freedom concerning an imaging angle owing to a mechanism including a C-arm and the like, an imaging angle determination device, a program storage medium, and a method.
2. Description of the Related Art
In diagnosis using an X-ray diagnostic apparatus, and more specifically, in diagnosis of a case of stricture, imaging needs to be performed such that the axial direction of a blood vessel does not become parallel to the depth direction (projection direction) of X-rays. Note that angles of the imaging angles of X-rays which are used for medical treatment and diagnosis are also called working angles. If, for example, imaging is performed while a blood vessel runs along the depth direction, since an X-ray image is a kind of shadowgraph, a projected image of the blood vessel is shorter than the actual blood vessel. This makes it impossible to perform proper measurement. This phenomenon is called shortening. Conventionally, imaging must be repeatedly performed at different angles.
In order to solve this problem, according to the prior art, blood vessels in a patient are imaged from a plurality of directions, and a three-dimensional image of the blood vessels is reconstructed on the basis of the resultant imaging data, thereby identifying a target blood vessel on the reconstructed three-dimensional image.
In order to obtain a three-dimensional image of blood vessels, the following methods are used: a method of using only data obtained in a very small number of directions, i.e., two or three directions, and a method of performing reconstruction on the basis of data obtained by performing imaging in many directions as in an X-ray computed tomography apparatus.
In the former method, it is necessary to associate corresponding positions between frames, and it is difficult to automate this. This operation always requires a doctor or technologist with rich clinical knowledge to perform designation, and hence hinders the flow of examination in some case. The latter method does not require such manual operation. However, complicated preparation is required for special imaging operation in this method, and a long processing time is needed after imaging operation. This may also hinder the flow of examination (see Jpn. Pat. Appln. KOKAI Publication No. 2004-020621).